Elastomer compositions with silane functionalized silica as reinforcing fillers

ABSTRACT

Certain embodiments described herein are directed to silane functionalized fillers that may be, for example, covalently coupled to a polymer. In some examples, devices that include the filler reinforced polymer compositions are also described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/335,086, filed Dec. 22, 2011.

FIELD

Examples disclosed herein relate generally to silica-reinforcedelastomer compositions. More particularly, certain embodiments disclosedherein are directed to silane coupling agents and/orsilane-functionalized fillers effective to covalently couple a filler toa polymer such as, for example, a fluoropolymer.

BACKGROUND

Fillers can be added to elastomer compounds and other polymers. However,limited reinforcement effect of fillers is achieved due to the weakinteractions between the fillers and the polymer.

SUMMARY

In one aspect, embodiments disclosed herein relate to a composition thatincludes a fluoropolymer covalently coupled to a filler through a silanecoupling agent, the silane coupling agent having a chemically similarreactive moiety as a cure site moiety of the fluoropolymer to which thesilane coupling agent is bonded.

In another aspect, embodiments disclosed herein relate to a method thatincludes reacting a filler with at least one silane coupling agenthaving the formula Q_(m)-Si—Z_(n), where Z comprises one or more groupsthat can provide covalent attachment to the filler, Q is —R″-G or—CR′₂—CR′—R″-G, where R′ is a hydrogen or a fluorine, R″ is optional andis a linear or branched C1-C18 alkyl group, optionally containing one ormore ether oxygen atoms and optionally fluorinated, G is a halogen, anitrile group, or a vinyl group, and the sum of m+n is equal to four tocovalently couple the silane to the filler; and reacting the covalentlycoupled silane-filler with a polymer to covalently couple the polymer tothe covalently coupled silane-filler.

In yet another aspect, embodiments disclosed herein relate to a silanecoupling agent having the formula of Q_(m)-Si—Z_(n), where Z is one ormore groups that can provide covalent attachment to a filler, Q is —R″-Gor —CR′₂—CR′—R″-G, where R′ is a hydrogen or a fluorine, R″ is optionaland is a linear or branched C1-C18 alkyl group, optionally containingone or more ether oxygen atoms and optionally fluorinated, G is ahalogen, a nitrile group, or a vinyl group, and the sum of m+n is equalto four.

In yet another aspect, embodiments disclosed herein relate to a movingor progressive cavity motor or pump assembly having an inlet end and anoutlet end, the motor or pump includes a housing and a rotor and astator disposed within the housing. The surface of the rotor or thestator is made of an elastomer material which permits a seal to formbetween contacting surfaces of the rotor and the stator. The elastomermaterial comprises a polymer covalently coupled to a filler through asilane coupling agent, the silane coupling agent having a chemicallysimilar reactive moiety as a cure site moiety of the fluoropolymer towhich the silane coupling agent is bonded

Additional aspects, examples, features and embodiments of the technologywill be apparent to the person of ordinary skill in the art, given thebenefit of the instant specification.

BRIEF DESCRIPTION OF THE FIGURES

Certain features, aspect and examples are described in more detail belowwith reference to the accompanying figures in which:

FIGS. 1A-1C show one process of covalently coupling a silane couplingagent to a surface of a filler, in accordance with certain examples;

FIG. 2 is an illustration of a filler particle covalently coupled to asilane coupling agent, in accordance with certain examples;

FIG. 3 is an illustration of a filler particle covalently coupled to apolymer through a silane coupling agent, in accordance with certainexamples;

FIG. 4 is an illustration of a thermally induced cure mechanism betweena polymer and a silane coupling agent covalently coupled to a fillerparticle;

FIGS. 5A-5C are illustrations showing particle dispersions and phases,in accordance with certain examples;

FIG. 6 shows a detailed view of a power section of a downhole motor; and

FIG. 7 is a cross-sectional view of the power section of the downholemotor, taken along section line 7-7 of FIG. 6

It will be recognized by the person of ordinary skill in the art, giventhe benefit of this disclosure, that the compounds shown in the figuresand used throughout the text may be shown with disproportionate bondlengths, bond angles and the like to facilitate a better understandingof the technology described herein. Unless otherwise specified, noparticular stereochemistry is implied in the illustrative chemicalcompounds drawn and described herein.

DETAILED DESCRIPTION

Certain examples described herein provide advantages over existingcoupling agents and/or fillers and materials produced using suchcoupling agents and/or fillers including, but not limited to, improvedelastic modulus stability at high temperature, reduction of the Payneeffect in fillers modified with the silane coupling agents (i.e.,reduced tangent delta), and increased use life of parts or componentsproduced using the materials disclosed herein. These and otheradvantages will be recognized by the person of ordinary skill in theart, given the benefit of this disclosure.

Certain embodiments of the polymers produced using the coupling agentsand/or fillers disclosed herein may be used in numerous industrial,medical and mechanical applications, and are particularly suited forenvironments where high temperature, high pressure, aggressive chemicalsand mechanical loads may be required or encountered. For example,certain embodiments of the cross-linked polymers may be particularlysuited for use in oil field service (OFS) industry such as, for example,the heavy oil market in: (1) structural component and insulationapplications such as electrical pads and cables, feed-through, housingand packaging material of electrical and chemical devices, valves,pumps, and etc.; (2) elastomeric applications: general-purpose sealsincluding o-rings and gaskets, packers for exploration and productiontools including mechanical packers, inflatable packers and swellablepackers, mud motor, actuators, cables and etc. Certain examples ofpolymers produced using the coupling agents and/or fillers and othermaterials disclosed herein may also be used in down-hole applicationssuch as chemical, wear, and heat resistant piping, sleeves, wire andcable jacketing, coatings, connectors, liners, tubes and similardevices. In addition, the polymers disclosed herein have additional usessuch as, for example, in snap fit parts, parts used in load bearingapplications, heat shrinkable molded parts, and other parts used in theelectrical, automotive, aerospace, medical industries and oil fieldservice industries.

In certain embodiments, the polymers produced using the coupling agentsand/or fillers disclosed herein may be used by themselves or incombination with one or more other polymers, metals or non-metals, orstructural components to provide an assembly configured for a desireduse. These and other applications and uses of the materials describedherein will be readily selected by the person of ordinary skill in theart, given the benefit of this disclosure.

The compositions produced using the silane functionalized fillersdescribed herein provide for covalent coupling of the polymer to thefiller through the silane functionalization. The term covalent couplingrefers to attachment through one or more covalent bonds but notnecessarily direct attachment to a particular species without anyintervening atoms. The fillers may be pre-modified with the silanefunctionalization prior to being compounded with the polymer or may bereacted with the silane during compounding.

Fillers used in fluoroelastomer compounds are different from those inconventional elastomers. Limited reinforcement effects of active fillersare observed due to the weak interactions at the interface of activefillers and fluoroelastomers. Non-active or low active carbon black ormineral fillers in loadings up to 50 phr may be used. In non-limitingexamples, MT-black N990 filler is used because of its large particlesize and low structure, as well as its lower pH that leads to shortercuring time. Other fillers including various grades of other carbonblacks, fibrous calcium silicate, barium sulfate, titanium oxide, ironoxide, silica, poly(tetrafluoroethylene) (PTFE) powders, etc., may alsobe used.

Strong interactions can be achieved at the filler-fluoropolymerinterface if the fillers are covalently bound to the polymers. Silanecoupling agents, which are capable of forming covalent bonds directly tothe polymer, can be used to enhance the adhesion between the polymer andthe fillers, such as silica fillers. The fillers may be pre-modifiedwith the silane coupling agents to possess silane functionalizationprior to being compounded with the polymer or the fillers may be reactedwith the silane coupling agent during compounding. In either case, thesilane may covalently bind the filler to the polymer and thus bereferred to a silane coupling agent. In embodiments, the silane couplingagent may possess at least one moiety that is the same as the reactiveor cure site monomer or moiety of the polymer being modified.

Certain embodiments described herein are directed to thermally stablesilane coupling agents which are effective to provide covalent bondingbetween silica fillers and fluoroelastomers, perfluoroelastomers,fluoroplastics and other polymers. The advantages provided in at leastcertain embodiments include, but are not limited to: (1) the reactivityof the cure site moiety in these silane coupling agents should be thesame as or chemically similar to the cure site moiety on the polymer sothat the silane coupling agent can react well with the polymer matrix toform cross-links providing a reinforcing effect; (2) the thermalstability of these silanes and the produced cross-links are excellent sothat reinforcing effect will be present even at high temperatures;and/or (3) similar to conventional coupling agents, these functionalsilanes can also improve the dispersion of silica fillers by changingtheir surface polarity.

In one embodiment, the silane coupling agents have a general structureas shown in formula (I):

Q_(m)-Si—Z_(n)  (I)

where Q comprises one or more groups that can provide covalentattachment to the polymer and Z comprises one or more groups that canprovide covalent attachment to the filler.

In certain embodiments, the Z group of formula (I) may be selected suchthat reaction with one or more groups on the filler surface results incovalent bond formation between the coupling agent and the filler. Incertain examples, Z may be a hydrolyzable group including, but notlimited to, a hydroxy, an alkoxy, an acyl-oxyl, a halogen, an amine orother suitable hydrolyzable group. In some examples, the Z group(s) maybe labile and cleaved or otherwise removed through dehydration or othersuitable mechanisms such that the Si group of formula (I) can covalentlybond to a surface moiety on the filler to covalently couple the silaneto the filler. For example, Z may be a hydroxyl group that can protonateand leave as water with subsequent or concurrent formation of a covalentbond between the filler and the coupling agent. In some examples, Z maybe an alkyl group comprising a hydroxyl group including, but not limitedto, methoxy, ethoxy, propoxy, butanoxy or other oxygen containing alkylgroups which may be saturated or unsaturated. In addition, where morethan one Z group is present, the Z group may be the same or may bedifferent.

The sum of m+n is normally equal to four, with each of m and nindependently selected from zero, 1, 2, 3 and 4. In some examples, n is3 and m is 1 or n is 2 and m is 2 or n is 1 and m is 3. It is alsopossible for m to be 4 and n to be zero or for m to be zero and n to be4 depending on the exact substituents selected for Q and Z.

As mentioned above, in embodiments, the silane coupling agent maypossess at least one moiety that is the same as or chemically similar tothe reactive or cure site moiety of the polymer being modified. Thiscure site moiety on the silane coupling agent may be represented as Q informula (I) above. The cure site moiety of the polymer being modifiedmay depend on the particular curing mechanism being used. For example, afree radial curing mechanism may require a cure site monomer, discussedbelow, to be incorporated into the polymer backbone to allow forcrosslinking. By having a similar moiety as the cure site monomerpresent in a silane coupling agent, the polymer may also form covalentbonds with the filler (through the silane coupling agent) during curingof the polymer. Cure site monomers may generally have the formulaCR′₂═CR′—R″-G, where R′ is a hydrogen or a fluorine, R″ is optional andmay be a linear or branched alkylene group, optionally containing one ormore ether oxygen atoms and optionally fluorinated, and G is a halogen,such as Br or I, a nitrile group, or a vinyl group. Thus, Q may have asimilar chemistry of —CR′₂—CR′—R″-G or —R″-G, where R′ is a hydrogen ora fluorine, R″ is a linear or branched C1-C18 alkyl group, optionallycontaining one or more ether oxygen atoms and optionally fluorinated,and G is a halogen, such as Br or I, a nitrile group, or a vinyl group.

For fluoropolymers not containing a cure site monomer, such as polymerscured by a bisphenol or diamine curative, curing may involvedehydrofluorination at a vinylidene fluoride site, followed bynucleophilic substitution by a hydroxy group of bisphenol or an amineaddition. Thus, in such cases, the silane coupling agent may include aterminal vinylidene fluoride group, i.e., Q may have a chemistry of—CR′₂—CR′—R″—CR′═CR′₂ or —R″—CR′═CR′₂, where R′ is a hydrogen or afluorine, R″ is optional and may be a linear or branched C1-C18 alkylgroup, optionally containing one or more ether oxygen atoms andoptionally fluorinated.

In certain embodiments, the silane coupling agent may take the form of acompound as shown in the below formulae:

In the above formulae, the Q group is shown to be based on reaction of asilane with CR′₂═CR′—R″-G containing a vinyl (or vinylidene fluoride)group. It is envisioned that the Q group on the silane may be the sameas the pendant group of the cure site monomer hanging off of the polymerbackbone, or the cure site monomer may be reacted with a silane (asshown above) through a vinyl or vinylidene fluoride group such thatthere additional C2 group within Q as compared to the pendant group ofthe cure site monomer extending from the polymer backbone and thus the Qgroup is the same as the cure site monomer chemistry (pre-polymerized).Further, while ethoxy groups are shown as the Z substituents in theabove formulae, it is intended that any Z group described above,including hydroxyl, alkoxy, acyl-oxyl, halogen and amine groups may beused, in any combination within a single coupling agent.

The silane coupling agent may be present in amounts ranging from 0.5 to25 parts per hundred parts of resin. In another embodiment, the silanecoupling agent may be present in an amount ranging from 0.1 to 5 partsper hundred parts of resin.

The illustrative examples of the silane coupling agents described hereinmay be synthesized using known methods of producing silane compounds.For example, halo- or alkoxysilanes may be reacted with Grignardreagents (RMgX where R is an organic group and X is a halogen) or alkalimetal organics, e.g., RLi where R is an organic group as shown in thereaction schemes below.

RMgCl+HSiCl₃--->RHSiCl₂+MgCl₂

RLi+SiCl₄--->RSiCl₃+LiCl

Another method of synthesizing silane coupling agents is throughhydrosilyation of an olefin in the presence of a catalyst such as, forexample, chrloroplastinic acid, t-butylperoxide and amine complexes. Thesilicon in general ends up on the least substituted carbon.

RCH═CH₂+HSiCl₃--->RCH₂CH₂SiCl₃

Hydrosilylation may occur, for example, in the presence of Karstedtcatalyst (Pt₂{[(CH2═CH)Me₂Si]₂O}₃) to silylate an unsaturated sidechain. In other examples, organosilanes may also be produced by directsynthesis of an organohalide with silicon using heat and a coppercatalyst.

RCl+Si--->RSiCl₃+R₂SiCl₂+R₃SiCl

In certain embodiments, the silane coupling agents may react with thefiller through various mechanisms. In one route, the silane may firstreact with additional silane coupling agents to provide a condensedproduct having polysiloxy linkages. Next, hydrogen bonding of the organogroup(s) of the silane to the surface of the filler may first occur.Protons from the surface may be donated to the organo groups of thecoupling agent followed by loss of water (dehydration) and subsequentlinkage between the filler surface and the silane may then occur withloss of water. An illustration of the overall process is shown in FIGS.1A-C using a generic silane.

Illustrative organo groups that may be used in the silane couplingagents include, but are not limited to, —SiCl₃, —SiBr₃, —SiF₃,—Si(OMe)₃, —Si(OEt)₃, —Si(OnPr)₃, —Si(OnBu)₃, —Si(OEtBu)₃, and —Si(OAc)₃where Me is methyl, Et is ethyl, nPr is n-proply, nBu is n-butyl, and Acis acetyl. The substituents of the silane group need not be the same. Insome examples, three of the substituents may be the same, two of thesubstituents may be the same or the three substituents may be different.It is desirable that the substituents of the silane be hydrolyzablegroups whether or not the substituents are the same or not.

In certain embodiments, to synthesize the silane coupling agentcompounds, the base structure may be hydrosilylated, e.g., a Q-Cl basestructure can be hydrosilylated. For example, hydrosilylation of Q-Clwith proper tri-functional (triethoxy, trimethoxy, or trichloro) silanesat the presence of Karstedt catalyst can provide the silane couplingagents.

In certain embodiments, by modifying the filler surface, differentproperties are achieved. First, the surface polarity of the silicafiller is dramatically changed. For example, before silanization, silicafillers (fumed or precipitated) have very high surface energy. They tendto form large agglomerates in a polymer matrix which often become thecrack-initiation sites and thus degrade the mechanical properties of thecomposites. When silica fillers are treated with silane coupling agents,their surface energy is lowered and it becomes similar to that offluoroelastomers. These modified fillers will absorb much less moisture,or even not absorb water vapor if complete silane coverage is achieved.As a result, the fillers will disperse well in fluoroelastomers whencompounded with fluoroelastomer gums. Second, the silanes are reactive.At the curing conditions of fluoroelastomers and etc., the cure sitemoiety of these silanes will react (leading to cross-links at the fillersurfaces) with the cure site moieties on the polymers and thus bind thefillers covalently to the polymers. For example, there may be covalentlybound rubber on the filler surfaces. The bound rubber can affect themechanical properties of rubbers.

When comparing bound rubber content and properties in different systemsor at different conditions for one particular polymer-filler system,several factors should be considered as bound rubber is sensitive to thechemical and physical nature of the polymers and fillers, as well as theexperimental conditions (temperature, solvent and etc.) at which thebound rubber is isolated and measured. Covalent bound rubber obtainedusing the silane coupling agents described herein is very different fromthat in polyolefin-carbon black systems where physical attractionstether the polymer layer near the filler surfaces. The bond dissociationenergies of silicon-oxygen, silicon-carbon and carbon-carbon (single)bonds, which are the major types of chemical bonds at the cure sitemoiety-silane series modified silica surface, are about 370-570 kJ/mol.As a comparison, the absorption energy of polyolefins on carbon blacksis in general about 10-35 kJ/mol (at least one order of magnitudeweaker). The exceptionally strong bonding present in the covalentlybound rubber can assist in providing excellent high-temperatureresistance of the polymer compounds.

In certain embodiments, the surface modification of silicate surfacesusing these silane coupling agents can be carried out by standardprocedures. The coupling agents can be applied to the substrates bydeposition from aqueous alcohol, deposition from aqueous solution, bulkdeposition onto powders by a spray-on method, integral blend method,anhydrous liquid phase deposition, vapor phase deposition, spin-ondeposition and spray application. For chlorosilanes, they can bedeposited from alcohol solution. Notwithstanding which particularapplication procedure may be selected, the reaction of the silanecoupling agents can be categorized into four steps for conveniencepurposes. First, hydrolysis of the three hydrolyzable groups occurs(water is present in the solvent or absorbed at the surface from air).Condensation to oligomers follows. The oligomers then form hydrogenbonds with hydroxyl group on the surface. Finally, during drying orcuring, a covalent linkage is formed with the substrate with concomitantloss of water. One example of the hydrolytic deposition of silanes isshown in FIGS. 1A-C. An illustration showing a cure sitemoiety-containing silane covalently coupled to the surface of a silicaparticle is shown in FIG. 2. In use, the silica filler is seldom presentas a single spherical particle as shown in FIG. 2. In many instances,the silica fillers arrange themselves similar to strings of pearls.

In certain embodiments, an excess of silane coupling agent may be usedsuch that substantially all accessible hydroxyl sites (or other reactivesites) on the filler surface can be modified with a silane couplingagent. In other examples, complete coverage with silane coupling agentsmay not be required. High-temperature silanes such asphenyltriethoxysilane, pentafluorophenyltriethoxysilane,p-tolyltrimethoxysilane,p-trifluoromethyltetrafluorophenyl-triethoxysilane and etc. can be mixedwith the silane coupling agents to dilute the surface concentration ofthe coupling silanes. These high-temperature silanes serve as coveringagents which modify the surface polarity of the fillers and do not formcovalent bonds to any substantial degree.

In certain examples, the exact filler used with the silane couplingagents is not of great consequence. In particular many different typesof fillers may be used, and in certain instances more than one type offiller may be used. Illustrative types of fillers that can be usedinclude, but are not limited to, silica, precipitated silica, amorphoussilica, vitreous silica, fumed silica, fused silica, quartz, glass,aluminum, aluminum-silicate (e.g., clays), copper, tin, talc, inorganicoxides (e.g., Al₂O₃, Fe₂O₃, TiO₂, Cr₂O₃), steel, iron, asbestos, nickel,zinc, silver, lead, marble, chalk, gypsum, barites, graphite, carbonblack, treated carbon black such as, for example, silicon treated carbonblack and other particles, powders and materials that include, or can bechemically modified to include, one or more surface reactive groups.Fumed silica Cab-o-Sil M5 (Cabot) is one example of a filler than can beused. Fillers may be incorporated in amounts ranging from about 1 to 50parts per hundred parts of resin. Some embodiments may use at least 2parts per hundred parts of resin, at least 5 parts per hundred parts ofresin, at least 10 parts per hundred parts of resin or at least 20 partsper hundred parts of resin.

Similar to the fillers, the exact polymer used with the silane couplingagents may vary. In one embodiment, polymers that include one or more ofa double bond, halogen, leaving groups or that can react by freeradical, amine curing, bisphenol curing, or thermal curing mechanismsmay be used with the silane coupling agents described herein.Illustrative polymers include, but are not limited to a high densitypolyethylene, a nylon, a polycarbonate, a polyether sulfone, apolyphenylene oxide, a polyphenylene sulfide, a polypropylene, apolystyrene, a polyurethane, a polysulfone, a polyvinylchloride, apolyamide, a polyimide, a polyamide-imide, a polybutylene, apolybutylene terphthalate, a polyepoxide and other polymers. In someexamples, a single type of polymer, different polymers, blends ofpolymers and the like may be used. Thus, in examples described hereinthat use a fluoropolymer in combination with a coupling agent, thefluoropolymer may be substituted with, or used in combination with, oneor more other polymers. In some examples, the coupling agent may beparticularly suited for use with polymers in high temperatureapplications such as, for example, those greater than or equal to about150° C.

In one embodiment, a halopolymer such as a fluoropolymer, achloropolymer, and a bromopolymer may be used. Mixed halo polymersincluding two or more different halo substituents, such as, for example,chlorofluoropolymers and bromofluoropolymers, may also be used.Halopolymers may also include heteroatoms including, but not limited to,nitrogen, oxygen, sulfur and heterogroups formed from nitrogen, oxygenand sulfur. Of particular interest for use with the cross-linkersdisclosed herein are fluoropolymers, which are difficult to cross-linkdue to the inertness of the carbon-fluorine bond. Fluoroelastomers ingeneral are synthesized by radical co-, ternary or tetrapolymerizationsof fluoroalkenes. Examples of fluoroelastomers include copolymerscomprising units of vinylidene fluoride (VDF or VF₂) and units of atleast one other copolymerizable fluorine-containing major monomer suchas tetrafluoroethylene (TFE), hexafluoropropylene (HFP),chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), ethylene (E),propylene (P), and a perfluoro(alkyl vinyl ether) (PAVE). Specificexamples of PAVE include perfluoro(methyl vinyl ether) (PMVE),perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether).Depending on the type of curing mechanism to be used, the polymer mayalso incorporate at least one cure site monomer therein to allow aradical to be formed by a peroxide and then crosslinked by a co-agent.Cure site monomers may be incorporated into fluoroelastomer in an amountranging from about 0.1 to about 10 (or from about 0.2 to about 5) weightpercent, based on the total composition of the fluoroelastomer. Theremaining units in the fluoroelastomers may be comprised of at least twodifferent copolymerized monomers, different from each other and saidcure site monomer, selected from the group consisting of fluoromonomers,hydrocarbon olefins and mixtures thereof. Fluoromonomers include bothfluorine-containing olefins (fluoroolefins) and fluorine-containingvinyl ethers (fluorovinyl ethers). Specific examples of fluoroelastomersthat may be employed (cure site monomers omitted for clarity) include,but are not limited to copolymerized units of TFE/PMVE, VF₂/PMVE,VF₂/TFE/PMVE, TFE/PMVE/E, TFE/P and TFE/P/VF₂.

Examples of suitable cure site monomers include, but are not limited to:i) bromine-containing olefins; ii) bromine-containing vinyl ethers; iii)iodine-containing olefins; iv) iodine-containing vinyl ethers; v)fluorine-containing olefins having a nitrile group; vi)fluorine-containing vinyl ethers having a nitrile group; and vii)non-conjugated dienes.

Brominated cure site monomers may contain other halogens, such asfluorine. Examples of brominated olefin cure site monomers arebromotrifluoroethylene (BTFE); 4-bromo-3,3,4,4-tetrafluorobutene-1(BTFB); vinyl bromide; 1-bromo-2,2-difluoroethylene; perfluoroallylbromide; 4-bromo-1,1,2-trifluorobutene-1;4-bromo-1,1,3,3,4,4-hexafluorobutene;4-bromo-3-chloro-1,1,3,4,4-pentafluorobutene;6-bromo-5,5,6,6-tetrafluorohexene; 4-bromoperfluorobutene-1 and3,3-difluoroallyl bromide. Brominated vinyl ether cure site monomers mayinclude 2-bromo-perfluoroethyl perfluorovinyl ether and fluorinatedcompounds of the class CF₂Br—R_(f)—O—CF═CF₂ (R_(f) is aperfluoroalkylene group), such as CF₂BrCF₂O—CF═CF₂CF₂═CFOCF₂CF₂CF₂OCF₂CF₂Br, and fluorovinyl ethers of the class ROCF═CFBror ROCBr═CF₂ (where R is a lower alkyl group or fluoroalkyl group) suchas CH₃OCF═CFBr or CF₃CH₂OCF═CFBr.

Suitable iodinated cure site monomers include iodinated olefins of theformula: CHR═CH-L-CH₂CHR—I, wherein R is —H or —CH₃; L is a C₁-C₁₈(per)fluoroalkylene radical, linear or branched, optionally containingone or more ether oxygen atoms, or a (per)fluoropolyoxyalkylene radicalas disclosed in U.S. Pat. No. 5,674,959. Other examples of usefuliodinated cure site monomers are unsaturated ethers of the formula:I(CH₂CF₂CF₂)_(n)OCF═CF₂ and ICH₂CF₂O[CF(CF₃)CF₂O]_(n)CF═CF₂, and thelike, wherein n=1-3, such as disclosed in U.S. Pat. No. 5,717,036. Inaddition, suitable iodinated cure site monomers including iodoethylene,4-iodo-3,3,4,4-tetrafluorobutene-1 (ITFB);3-chloro-4-iodo-3,4,4-trifluorobutene;2-iodo-1,1,2,2-tetrafluoro-1-(vinyloxy)ethane;2-iodo-1-(perfluorovinyloxy)-1,1,-2,2-tetrafluoroethylene;1,1,2,3,3,3-hexafluoro-2-iodo-1-(perfluorovinyloxy)propane; 2-iodoethylvinyl ether; 3,3,4,5,5,5-hexafluoro-4-iodopentene; andiodotrifluoroethylene are disclosed in U.S. Pat. No. 4,694,045. Allyliodide and 2-iodo-perfluoroethyl perfluorovinyl ether may also be usefulcure site monomers.

Useful nitrile-containing cure site monomers may include those of theformulas shown below. CF₂═CF—O(CF₂)_(n)—CN where n=2-12;CF₂═CF—O[CF₂—CF(CF₃)—O]_(n)—CF₂—CF(CF₃)—CN where n=0-4;CF₂═CF—[OCF₂CF(CF₃)]_(x)—O—(CF₂)_(n)—CN where x=1-2, and n=1-4; andCF₂═CF—O—(CF₂)_(n)—O—CF(CF₃)CN where n=2-4.

Examples of non-conjugated diene cure site monomers include, but are notlimited to 1,4-pentadiene; 1,5-hexadiene; 1,7-octadiene;3,3,4,4-tetrafluoro-1,5-hexadiene; and others, such as those disclosedin Canadian Patent 2,067,891 and European Patent 0784064A1. A suitabletriene is 8-methyl-4-ethylidene-1,7-octadiene.

Of the cure site monomers listed above, for situations wherein thefluoroelastomer will be cured with peroxide, brominated or iodinatedcure such monomers such as 4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB);4-iodo-3,3,4,4-tetrafluorobutene-1 (ITFB); allyl iodide;bromotrifluoroethylene, or a nitrile-containing cure site monomer suchas perfluoro(8-cyano-5-methyl-3,6-dioxa-1-octene) may be used. When thefluoroelastomer will be cured with a polyol, 2-HPFP orperfluoro(2-phenoxypropyl vinyl) ether may be used. When thefluoroelastomer will be cured with a tetraamine, bis(aminophenol) orbis(thioaminophenol), a nitrile-containing cure site monomer (e.g.,8-CNVE) may be used. When the fluoroelastomer will be cured with ammoniaor a compound that releases ammonia at curing temperatures (e.g., urea),a nitrile-containing cure site monomer (e.g., 8-CNVE) may be used.Further, it is also within the scope of the present disclosure thatother cure site monomers may be used, where the silane coupling agentwould possess the same type of chemical moiety for its Q group as theselected cure site monomer.

Some embodiments may involve a silane coupling agent having a chemicallyidentical Q group as the cure site moiety on the polymer. Someembodiments may involve a silane coupling agent having a chemicallyidentical Q group as the pendant group of the cure site monomer. Otherembodiments may involve a silane coupling agent having a chemicallysimilar Q group as the pendant group of the cure site monomer, i.e., ifthe cure site monomer is a bromine-containing olefin, such as thosedescribed above, the Q group may be any bromine-containing alkyl group.

In certain embodiments, fluoroelastomers can also be produced in anemulsion polymerization process using a water-soluble polymerizationinitiator and an excess amount of surfactant. The resultingfluoroelastomer may exit the reactor in the form of a latex which isdegassed (e.g., freed from unreacted monomers), coagulated, filtered andwashed. Fluoroelastomers can also be produced in a suspensionpolymerization process, where polymerization is carried out bydispersing one or more monomers, or an organic solvent with monomerdissolved therein, in water and using an oil-soluble organic peroxide.No surfactant or buffer in general is used and fluoroelastomer isproduced in the form of polymer particles which may be directlyfiltered, e.g., without the need for coagulation, and then washed, thusproducing a cleaner polymer than that resulting from an emulsionprocess. Also, the fluoroelastomer polymer chains are substantially freeof ionic end groups so that the Mooney viscosity is relatively low andthe polymer has improved processability compared to polymer produced byan emulsion process.

In certain embodiments, perfluoroelastomers can be used with the silanemodified fillers described herein. Perfluoroelastomers are generallyamorphous polymeric compositions having copolymerized units of at leasttwo principal perfluorinated monomers. Generally, one of the principalmonomers is a perfluoroolefin while the other is a perfluorovinyl ether.Representative perfluorinated olefins include tetrafluoroethylene andhexafluoropropylene. Suitable perfluorinated vinyl ethers include thoseof the formula CF₂═CFO(R_(m)O)_(n)(R_(k)O)_(j)R_(f) where R_(m) andR_(k) are different linear or branched perfluoroalkylene groups of 2-6carbon atoms, m, n and j are independently 0-10, and R_(f) is aperfluoroalkyl group having 1-6 carbon atoms. Perfluoroelastomers haveachieved outstanding commercial success and are used in a wide varietyof applications in which severe environments are encountered, inparticular those end uses where exposure to high temperatures andaggressive chemicals occurs. For example, these polymers are often usedin seals for aircraft engines, in oil-well drilling devices, and insealing elements for industrial equipment used at high temperatures. Theoutstanding properties of perfluoroelastomers can be attributed to thestability and inertness of the copolymerized perfluorinated monomerunits that make up the major portion of the polymer backbones in thesecompositions. Such monomers include tetrafluoroethylene andperfluorinated vinyl ethers. In order to develop elastomeric propertiesfully, perfluoroelastomers are in general cross-linked, e.g.,vulcanized. To this end, a small amount of cure site monomer can becopolymerized with the perfluorinated monomer units.

In other embodiments, poly(perfluoro-alkylene oxides) terminated withpolymerizable functional groups can be polymerized to prepare certainpolymers, e.g., polyurethanes, having low glass transition temperaturesand low-temperature flexibility. For example, poly(perfluoroalkyleneoxide) peroxides can be used with ethylenically unsaturated monomers inmaking block copolymers having good low-temperature flexibility.Fluorinated ethers with nonfunctional terminal moieties are sold underthe trademarks “Krytox” and “Fomblin” for use as vacuum pump fluids, seee.g., G. Caporiccio et al., 21 IND. ENG. CHEM. PROD. RES. DEV. 515-19(1982).

In certain examples, compositions of fluoroelastomers cross-linked withdihydroxypolyfluoroethers may be used. The dihydroxypolyfluoroethers maycontain either branched moieties, are random copolymers containing—CF₂O— repeating units or contain partially fluorinated repeat units. Inother examples, perfluoropolyether polymers may be prepared asdescribed, for example, in U.S. Pat. No. 5,026,786. Theseperfluoropolyethers comprise randomly distributed perfluoroxyalkyleneunits. European Pat. Pub. No. 222,201 describes vulcanizable rubberblends comprising certain perfluoropolyether which can also be used withthe coupling agents described herein. These perfluoropolyethers havebrominated or fluorinated end groups. European Pat. Pub. No. 310,966describes rubber blends comprising certain perfluoropolyethers. Theseperfluoropolyethers comprise perfluoroalkyl end groups.

In certain embodiments, certain classes of fluorinated ethercompositions comprising functional fluoroaliphatic mono- and polyethersmay be used, as described, for example, in U.S. Pat. Nos. 5,384,374 and5,266,650.

The polymers suitable for use with the silane modified fillersincluding, but not limited to, fluoroelastomers, perfluoroelastomers andthe like, are commercially available from numerous sources including,but not limited to, DuPont Performance Elastomers LLC (Wilmington,Del.), DuPont-Mitsui Fluorochemicals Co. (Japan), AGC Chemicals America(Exton, Pa.), Solvay Solexis (Italy), Daikin Industries (Japan), ZeonCorporation (Japan), Exfluor Research Corporation (Austin, Tex.) andother chemical suppliers.

In preparing the compositions, the silane coupling agent may be linkedto the filler surface in a first step and the resulting product can bereacted with the polymer in a second step. In other examples, the silanecoupling agent may be reacted with the polymer in a first step and thenreacted with the filler surface in a second step. In yet other examples,the polymer, filler and silane coupling agent may be mixed or blendedtogether to provide a composition that includes a polymer coupled to afiller through the silane coupling agent. Notwithstanding the exactsequence of event used, the resulting composition includes a fillercovalently coupled to a polymer through the silane coupling agent. Anillustration of the resulting composition is shown in FIG. 3.

In certain examples, free radicals are first generated using suitablespecies such as, for example, branched alkyl molecules including one ormore heteroatoms such as, oxygen, nitrogen or sulfur. In this initiationstep, the free radicals may be generated by exposing the alkyl moleculesto light, heat, initiators such as peroxides (organic peroxides whichare particularly effective curing agents for fluoroelastomers includedialkyl peroxides which decompose at a temperature above 50° C.),chlorine gas, bromine or other commonly employed free radicalinitiators. The formed free radicals may react with the silane-modifiedfillers to form silane-modified fillers that include a free radical. Thefree radical filler can react with the polymer in one or a series ofpropagation steps to covalently couple the polymer to the silanemodified filler and/or to generate more free radicals. In one or moretermination steps, the free radical filler may react with multiplepolymer molecules and result in polymer being covalently coupled to thefiller through the silane coupling agent. Such free radical reactionsand conditions suitable for performing them will be readily selected bythe person of ordinary skill in the art, given the benefit of thisdisclosure.

As mentioned above, curatives used in forming the present compositionsmay include peroxides, amine curatives and polyhydroxy (e.g., bisphenol)curatives. In general, the curative may be used in amounts of from about0.5-5 parts by weight per hundred parts by weight resin (phr).

Example peroxide curatives may include tert-butylcumyl peroxide (e.g.,Trigonox® T), 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (e.g., Trigonox®101), alpha,alpha-bis(tert-butylperoxy-isopropyl)benzene (Perkadox®14/40 and Perkadox® 14 (without carrier)), and2,5-dimethyl-2,5-di(t-butyl-peroxy)hexane (Varox.® DBPH-50 or Varox®DBPH (liquid form)).

A co-agent may be used in combination with the peroxide curative. Someco-agents for peroxide curing of fluoroelastomers include, but are notlimited to, triallylisocyanurate (TAIC), trimethallylisocyanurate(TMAIC) and triallylcyanurate (TAC), triacrylformal, triallyltrimellitate, N,N′-m-phenylenebismaleimide, diallyl phthalate,tetrallylterephthalamide, tris(diallylamine)-s-triazine, triallylphosphate, N,N,N′,N′-tetrallyl-malonamide; trivinyl-isocyanurate;2,4,6-trivinyl-methyltrisiloxane;N,N′bisallylbicyclo-oct-7-ene-disuccinimide (BOSA), andN,N-diallylacrylamide. Generally, the co-agent may be used in an amountof 0.1 to 10 parts by weight per 100 parts by weight of resin.

Examples of amine curatives are organic aliphatic or aromatic diaminessuch as ethylenediamine or hexamethylenediamine, or their carbamates,hydrochlorides, oxalates, or reaction products with hydroquinone.Specific examples include hexamethylene diamine carbamate, such as DIAK(trademark of DuPont Dow Elastomers) no. 1, dicinnamylidene diaminecarbamate, such as DIAK no. 3, and 4,4′-bis(aminocyclohexyl)-methanecarbamate, such as DIAK no. 4. Examples of bisphenol curatives arefluorinated bisphenol A, 4,4′-hexafluoroisopropylidene diphenol (i.e.,bisphenol AF) and derivatives thereof. Other polyhydroxy compounds mayalso be used.

In some instances, the compositions may be cured without the addition ofa curative, but by thermal curing. For example, crosslinking may bethermally induced in nitrile-containing elastomers by formation of atriazine ring, between nitriles in the polymer and/or present within theQ group of a silane coupling agent, as illustrated in FIG. 4.

Additional components may be used in or with the polymer-silane couplingagent-filler composition. For examples, additives, viscosity modifiers,processing aids and the like may be used. Examples of such additionalcomponents include, but are not limited to, antiozonants, antioxidants,plasticizers, resins, flame retardants, lubricants, one or more curingagents such as, for example, sulfur, sulfur donors, activators,accelerators, peroxides, thickeners, thinners, solvents, salts and othermaterials.

In processing the materials, various devices such as mills, mixers,molds, calendering devices, extruders and the like may be used. Forexample, the materials may be blended, open milled, mixed with aninternal mixer (which may include temperature control to avoidscorching) or otherwise combined in a suitable device. One pass ormulti-pass mixing may be used. High shear mixing may be used to obtaingood dispersion. The materials may be reworked in one or more additionalstages to further assist in mixing. Illustrative molding processes thatmay be used with the materials include, but are not limited tocompression, transfer and injection molding, extrusion and calendering.In compression molding, a preform may be used to provide a desired shapeor mass to the resulting material. In injection molding, the materialmay be injected at high pressure into a mold. Calendering may be used toproduce sheets of material. The compounds for calendaring may be usedwith viscosity modifiers to provide medium or low viscosity materials tofacilitate the calendaring process. The materials may also be shaped byextrusion. For example, the material may be forced through a shaping diebelow a curing temperature to impart a desired shape. Release agents maybe used in the preforms, molds and other parts to facilitate removal ofthe compressed or produced material from these devices.

The presence of a silane on the surface of the filler can have a greateffect on the filler dispersion and resulting mechanical properties ofthe composition. FIGS. 5A, B and C are schematic views of a polymerfilled with the thermally stable silane coupling agent modified silicaat different filler concentrations. FIG. 5A shows the local structure ofone cluster formed by primary silica aggregates. FIG. 5B showsaggregated filler clusters below the gel point Φ*, and FIG. 5C showsaggregated filler clusters above the gel point Φ*. By modifying thesurface of the filler with a silane, and subsequent coupling to apolymer through the silane, a reduction in the Payne effect (also knownas the Fletcher-Gent effect) may be achieved. The Payne effect is thenon-linearity appearing at small strains (a few tens to a few % strain)due to breakage of the filler three-dimensional network. When the strainis removed or reduced back to the original level, the network reformsand this process generates a hysteresis. The hysteresis generates heatthat can be detrimental for the component lifetime. Adding a silanecoupling agent to the filler surface and covalently coupling themodified filler to the polymer can reduce this hysteresis and thereforeenergy dissipation, which in turn can increase the overall use life ofthe part or component that is produced from the material.

In certain examples, the compositions disclosed herein may be used indownhole tools and devices such as packers used in extraction of fuelsthrough a wellbore. For example, downhole tools, such as modularwireline tools or drilling tools with evaluation capabilities, thatemploy probes for engaging the formation and establishing fluidcommunication may be used to make the pressure measurements and acquirethe fluid samples. Fluid in general is drawn into the downhole toolthrough an inlet in the probe. In some instances, such as for tight, lowpermeability, formations, sampling probes are often replaced by dualinflatable packer assemblies. Examples of such probe and packer systemsare depicted, for example, in U.S. Pat. Nos. 7,392,851, 7,363,970,7,331,581, 6,186,227, 4,936,139, 4,860,581 and 4,660,637 and assigned toSchlumberger, the entire contents of which are hereby incorporatedherein by reference for all purposes. In one configuration, a packercomprises, for example, a resilient element, a housing and a rupturedisk. The resilient element is adapted to seal off an annulus of thewell when compressed, and the housing is adapted to compress theresilient element in response to a pressure exerted by fluid of theannulus on a piston head of the housing. The housing includes a port forestablishing fluid communication with the annulus. The rupture disk isadapted to prevent the fluid in the annulus from entering the port andcontacting the piston head until the pressure exerted by the fluidexceeds a predefined threshold and ruptures the rupture disk. In anotherconfiguration, dual packer elements may be used with either or both ofthe packer elements comprising one or more of the materials describedherein. For example, packer elements may be spaced apart along adownhole tool conveyed by a wireline in a borehole penetrating asubsurface formation. Although a wireline tool is illustrated, otherdownhole tools conveyed by drill string, coiled tubing, etc., are alsosuited for such tasks. When inflated, the packer elements cooperate toseal or isolate a section of the borehole wall, thereby providing a flowarea with which to induce fluid flow from the surrounding formation(s).Other packers and elements of packer assemblies may be produced usingone or more of the compositions described herein. In one embodiment, thecompositions may be used in a swellable packer for open-hole zonalisolation. For example, a fluoroelastomer composition as describedherein can be used as the barrier coating for swellable materials toslow down the rate of swelling.

In certain embodiments, the compositions disclosed herein may be used tocoat one or more devices such as, for example, a coating on the statoror rotor of a mud motor. For example, the composition may be used in amotor that imparts rotational drive to a drilling assembly. Illustrativemud motors and assemblies using them are described, for example incommonly assigned U.S. Pat. Nos. 7,289,285, 6,419,014, 5,727,641,5,617,926, 5,311,952, the entire disclosure of each of which is herebyincorporated herein by reference for all purposes. Referring now toFIGS. 6 and 7, an example mud motor using compositions of the presentdisclosure is shown.

FIGS. 6 and 7 show details of the power section 18 of a conventionaldownhole motor. The power section 18 generally includes a tubularhousing 22 which houses a motor stator 24 within which a motor rotor 26is rotationally mounted. The power section 18 converts hydraulic energyinto rotational energy by reverse application of the Moineau pumpprinciple. The stator 24 has a plurality of helical lobes, 24 a-24 e,which define a corresponding number of helical cavities, 24 a′-24 e′.The rotor 26 has a plurality of lobes, 26 a-26 d, which number one fewerthan the number of stator lobes and which define a correspondingplurality of helical cavities 26 a′-26 d′. In accordance withembodiments, the stator 24 and/or rotor 26 are formed of an elastomericmaterial having a composition of the present disclosure that providesthe lobe structure of the stator and/or rotor. The rotor and stator aredimensioned to form a tight fit (i.e., very small gaps or positiveinterference) under expected operating conditions, as shown in FIG. 6.Other embodiments may use an elastomeric rotor. The rotor 26 and stator24 form continuous seals along their matching contact points whichdefine a number of progressive helical cavities. When drilling fluid(mud) is forced through these cavities, it causes the rotor 26 to rotaterelative to the stator 24. During drilling, the mud motor elastomers ingeneral experience severe mechanical stress and deformation (mainlydynamic), aggressive downhole fluids, and high temperature and highpressure. The compositions of the present disclosure may possess silanes(and derived crosslinks) having an improved thermal stability so thatreinforcing effect of the fillers will be present even at hightemperatures (e.g., temperatures greater than 150° C., which isconsidered the upper limit for conventional elastomers used in mudmotors).

In certain examples, the compositions described herein may be used in aformation tester such as MDT (Modular Formation Dynamics Tester) fromSchlumberger, permeability probes, power drive pads and other componentsand tools commonly used downhole for oilfield and gas exploration.

When introducing elements of the examples disclosed herein, the articles“a,” “an,” “the” and “said” are intended to mean that there are one ormore of the elements. The terms “comprising,” “including” and “having”are intended to be open-ended and mean that there may be additionalelements other than the listed elements. It will be recognized by theperson of ordinary skill in the art, given the benefit of thisdisclosure, that various components of the examples can be interchangedor substituted with various components in other examples.

Although certain aspects, examples and embodiments have been describedabove, it will be recognized by the person of ordinary skill in the art,given the benefit of this disclosure, that additions, substitutions,modifications and alterations of the disclosed illustrative aspects,examples and embodiments are possible.

What is claimed is:
 1. A method comprising: reacting a filler with atleast one silane coupling agent having the formula Q_(m)-Si—Z_(n), whereZ comprises one or more groups that can provide covalent attachment tothe filler, Q is —R″-G or —CR′₂—CR′—R″-G, where R′ is a hydrogen or afluorine, R″ is optional and is a linear or branched C1-C18 alkyl group,optionally containing one or more ether oxygen atoms and optionallyfluorinated, G is a halogen, a nitrile group, or a vinyl group, and thesum of m+n is equal to four to covalently couple the silane to thefiller; and reacting the covalently coupled silane-filler with a polymerto covalently couple the polymer to the covalently coupledsilane-filler.
 2. The method of claim 1, further comprising forming freeradicals of the polymer during the reacting the covalently coupledsilane-filler with a polymer to couple the polymer at unsaturated sitesof the silane of the covalently coupled silane-filler.
 3. The method ofclaim 2, further comprising reacting the filler with the at least onesilane until substantially all surface sites of the filler comprise thesilane coupling agent.
 4. The method of claim 3, further comprisingreacting the filler with the at least one silane coupling agent in thepresence of an initiator.
 5. The method of claim 1, further comprisingprocessing the covalently coupled polymer-silane-filler using one ormore of a mixer, a mill, a mold, a calendering device and an extruder.6. A silane coupling agent having the formula of Q_(m)-Si—Z_(n), where Zcomprises one or more groups that can provide covalent attachment to afiller, Q is —R″-G or —CR′₂—CR′—R″-G, where R′ is a hydrogen or afluorine, R″ is optional and is a linear or branched C1-C18 alkyl group,optionally containing one or more ether oxygen atoms and optionallyfluorinated, G is a halogen, a nitrile group, or a vinyl group, and thesum of m+n is equal to four.
 7. The silane coupling agent of claim 6, inwhich Z is selected from a hydroxy, an alkoxy, an acyl-oxyl, a halogenand an amine.
 8. The silane coupling agent of claim 6, selected from thefollowing formulae: